how can i delete photos from google but not from Apple icloud

Firstly, I would suggest you check that the photos you have on Google Photos are available on your phone. If it is available on your phone, you can proceed to Google Photos on the web to delete these photos from Google, otherwise I would suggest you download the photos onto your computer or phone before proceeding with the deletion from Google Photos.

Initiating a deletion on Google Photos will not affect the pictures you have locally on your phone since you've mentioned that the syncing process between Google Photos and your phone has been stopped. Assuming that you are using an iPhone (since you have posted this question on Apple Community), you can also delete the Google Photos app (again, assuming you are using this official app for backups to Google Photos) to prevent future uploads to Google Photos.